The present invention concerns improvements in sliding gate valves for use in the pouring of molten metals.
Such valves are well established in the art and normally include a set of orificed refractory valve bodies which are maintained in mutual face-to-face contact with such contact being assisted by the biasing effect produced by springs for pressing the bodies together. The valve bodies are relatively movable to place the orifices in the respective bodies either into or out of registry with one another in order to control the flow of molten metal through the valve.
For the proper functioning of such valves, it is necessary that the seal pressure developed by the spring-biased contact between the plates be accurately and consistently applied. If the spring forces are too low, metal may creep between the contact faces of the valve bodies resulting in leakage or breakout of molten metal at considerable risk to the safety of workers in the area as well as to the integrity of the valve and the costly refractory valve bodies therein. Should the spring forces be set too high, the springs may be overstressed and the valve bodies distorted or otherwise degraded.
The accuracy of the application of seal pressure between the refractory valve bodies is adversely affected, especially in small gate valves of the kind normally operated manually to which the present invention has particular application, by the possibility of a foundryman to mishandle a valve actuator, which may comprise a lengthy crowbar, in such a way that he to some degree overcomes the spring force urging the valve bodies into leak-tight contact. It is also adversely affected by the need for frequent disassembly of such valves for purposes of inspecting and/or renewal of worn valve bodies in which extreme care must be taken in re-setting the spring forces upon restoration of the valve to its former operating condition.
It is toward the solution of the aforementioned problems therefore that the present invention is directed.